Device for regulating the flow of a fluid, in particular for solenoid valves

ABSTRACT

A device (RF) for regulating and/or stabilizing the flow of a fluid comprises a single body ( 20 ), envisaged for insertion in a pipe for passage of the fluid, in particular the inlet pipe of a solenoid valve ( 1 ). According to the invention, in the single body ( 20 ) of the device there is directly integrated an arrangement for silencing the flow of the fluid. The single body ( 20 ) is made in a single piece of moulded thermoplastic material.

The present invention relates to a device for regulating the flow of a fluid, in particular for solenoid valves, of the type indicated in the preamble of the attached claim 1.

In the sector of electrical household appliances, as well as in other applications, there is a widespread use of devices aimed at regulating and stabilizing the flow of a liquid, known generically by the name of flow regulators.

Known flow regulators usually comprise a cylindrical body made of plastic material, which defines an axial passage for the liquid, and supporting means, set at one end of said passage, for supporting an elastically deformable membrane. Said membrane, when subjected to the action of the flow, undergoes deformation in a pre-defined way so as to regulate the passage of the liquid and the corresponding flow rate.

The body of the flow regulator is usually positioned within the inlet connection of a solenoid valve during fabrication of the latter.

The presence of the flow regulator is often the cause of a troublesome noise, which is noticed during passage of the flow of the liquid, following upon opening of the solenoid valve. In order to limit said drawback, there have thus been proposed purposely built silencing inserts, designed to be mounted in said inlet connection, between the flow regulator and the system for opening/closing the solenoid valve.

A typical example of functional combination between a flow regulator and a silencing insert is described in EP-B-0 356 057, to which the reader is referred also for a more detailed discussion of the problems linked to the noise induced by flow regulators, as well as for possible technical solutions to said problem.

The arrangement according to the known art proves costly, both because the flow regulator and the corresponding silencing insert are components that have to be produced separately and because, in the subsequent assembly step, there have to be envisaged two distinct operating steps for assembly of each of the two components.

The regulator and the insert are typically held in position just by interference with the internal surface of the pipe which houses them. The relative positioning of the two components can occasionally be modified by the flow and/or by pressure jumps, with possible alteration of their pre-defined functional characteristics.

The purpose of the present invention is to overcome the aforesaid drawbacks by means of a new flow-regulator device of simple construction, reliable operation, and above all contained cost both in terms of production and in terms of assembly.

The above and yet other purposes are achieved, according to the present invention, by a device for regulating and/or stabilizing the flow of a fluid having the characteristics of claim 1, as well by a method for regulating and/or stabilizing the flow of a fluid having the characteristics of claim 36.

Further purposes, characteristics and advantages of the present invention will emerge clearly from the ensuing detailed description and from the annexed drawings, which are provided purely by way of explanatory and non-limiting example and in which:

FIG. 1 is a lateral cross section of a solenoid valve equipped with a flow regulator according to the present invention;

FIG. 2 is a top plan view of a flow regulator according to the invention;

FIG. 3 is a cross-sectional view according to the line III-III of FIG. 2;

FIG. 4 is a plan view similar to that of FIG. 2, but in which the flow regulator according to the invention is without one of its functional elements;

FIG. 5 is a plan view from beneath of a flow regulator according to the invention;

FIGS. 6 and 7 are two partially sectioned perspective views of the flow regulator of FIGS. 2 to 5;

FIG. 8 is a perspective view of the flow regulator of FIGS. 2 to 5, but without one of its functional elements;

FIGS. 9, 10 and 11 are, respectively, a perspective view, a top plan view and a plan view from beneath of a flow regulator, without one of its functional elements, built according to a first possible variant embodiment of the invention;

FIGS. 12, 13 and 14 are, respectively, a perspective view, a top plan view and a plan view from beneath of a flow regulator, without one of its functional elements, built according to a second possible variant embodiment of the invention;

FIG. 15 is a partially sectioned perspective view of a flow regulator built according to a third possible variant embodiment of the invention;

FIG. 16 is a perspective view of the flow regulator of FIG. 15 without one of its functional elements; and

FIG. 17 is a top plan view of the flow regulator FIGS. 15 and 16.

In FIG. 1, the reference number 1 designates, as a whole, a solenoid valve of the unbalancing type, or of the type servo-assisted by the pressure of the liquid, which integrates a flow-regulator device built according to the present invention. It may be assumed, by way of non-limiting example, that the solenoid valve 1 will be used for controlling the delivery of water to a generic washing machine for domestic purposes.

The solenoid valve 1 has a main body 2 comprising an inlet pipe 3, which can be connected by means of a pipe (not illustrated) to a tap of the water mains, and an outlet pipe 4, which can be connected to the washing machine. Associated to the body 2 is a flange 5, for fixing to the washing machine.

Within the inlet pipe 3 is housed a flow regulator built according to the invention, designated, as a whole, by RF. Said regulator RF is set downstream of a filter 6 of a type in itself known.

The solenoid valve 1 comprises a solenoid 7 made up of an induction coil consisting of an electrically conductive wire wound on a hollow bobbin 7A and provided with a magnetic yoke 8. The ends of the induction coil are electrically connected to two supply terminals, one of which is visible in FIG. 1 and is designated by 9.

The reference number 10 designates a first open/close element or plug inserted in one end of a mobile core 11 of the solenoid 7. The number 12 designates a passage or central hole present in a support or cup 13, which is integral with a second open/close element or membrane 14, the latter being constrained along its outer diameter between the body 2 of the solenoid valve 1 and an element 15 in which the mobile core 11 is positioned. When the solenoid 7 is not supplied at its electrical terminals 9, the plug 10, by means of the mobile core 11, is held by a spring 16 in the position for closing the hole or central passage 12.

The membrane 14 has calibrated holes, which, in combination with a respective passage made in the cup 13, are designed to set in communication an area A of the pipe 3 extending between the regulator RF and the membrane 14 with a chamber C delimited between the membrane 14 and the element 15. The aforementioned calibrated holes of the membrane 14 and the aforesaid pipes of the cup 13 are not shown in the figure.

The aforesaid hole or passage 12 made in the cup 13 enables, instead, the area A to be set in communication with the outlet connector 4 when the mobile core 11 is operated by the solenoid 7 in order to create a reduction in the pressure inside the chamber C such as to enable actuation of the valve 1 into the opening condition under the thrust of the incoming fluid, in accordance with the prior art. It is to be noted that the aforesaid reduction in the pressure may occur by virtue of the fact that the cross section of the passage of the hole 12 is greater than the sum of the cross sections of the individual calibrated holes in the membrane 14. The solenoid 7 is enclosed within a protective coating 17 obtained by moulding of thermoplastic material and fitted on the element 15. The latter has a threaded part, which is screwed into a threaded open seat made in the body 2 of the solenoid valve 1.

The flow regulator RF is illustrated in various views in FIGS. 2 to 8. In this connection, it is to be noted that in FIGS. 4 and 8 (as also in the subsequent FIGS. 9 to 14 and FIGS. 16 and 17) the said regulator is represented without its own membrane for regulating the flow (hereinafter designated by 26).

The flow regulator RF is of the variable-section type, which exploits deformation of an elastically deformable membrane, which is subjected to the action of the flow for self-regulation of passage of the liquid. According to the main aspect of the present invention, the body itself of the regulator RF is shaped for silencing the flow of the liquid that passes.

In the non-limiting example of FIGS. 2 to 8, the flow regulator RF has a body 20 with a substantially cylindrical outer wall, designated by 21. From an intermediate area of the wall 21 there branches off, towards the inside of the body 20, an annular wall, designated by 22A, which extends substantially at right angles to the cylindrical wall 21. From the internal end of the annular wall 22A, there then branches off a tubular wall 22B, which extends towards the bottom end of the body 20, basically at right angles to the annular wall 22A.

As may be appreciated from FIG. 3, in the embodiment provided by way of example, the internal diameter of the outer wall 21 decreases progressively from the top end of the body 20 up to the annular wall 22A. Instead, the internal diameter of the outer wall 21 increases progressively from the annular wall 22A up to the bottom end of the body 20.

The tubular wall 22B, which has an external diameter that decreases progressively, terminates in a bottom wall 23 of the body 20, which extends substantially parallel to the stretch of annular wall 22A.

From the bottom wall 23, there rises centrally a substantially circular second wall, which is designed to form a pin 24 having a substantially cylindrical shape and having an internal blind hole. From the bottom wall 23, along said circular wall or pin 24, there also rise two distinct supports 25. As may be noted (see, for instance FIGS. 4, 6 and 8), the supports 25 have a cross section shaped substantially like an arc of circumference and are formed in areas set opposite with reference to the pin 24.

As may be noted (see, in particular, FIGS. 4 and 6 to 8), between the side surface of each support 25 and the inner surface of the wall 21, there extends a respective baffle or radial diaphragm designated by 25A.

The reference number 26 designates an elastically deformable membrane having an annular shape, the central hole 26A of which is fitted on the pin 24. The membrane 26 is positioned so that the part of its bottom surface close to the central hole 26A is resting on the top surface of the supports 25. Maintenance of the position of the membrane 26 on the pin 24 is guaranteed by the presence of lateral retention appendages 24A defined on the end of the pin itself.

The reference number 27 designates projections or spacers having a circular cross section, which rise with calibrated height and distribution from the wall 22 to provide resting points for the part of the bottom surface of the membrane 26 close to the external diameter of the latter. In accordance with the known art, the projections 27 have the function of pre-determining the value of the flow rate of liquid at which the regulator RF intervenes.

Finally, the reference number 28 designates through holes of smaller cross section than that of the chamber S, i.e., the chamber which extends between 22B and 24-25. The holes 28 are defined in the area of the bottom wall 23 not occupied by the pin 24 and by the supports 25. According to the invention, the holes 28 preferably have a non-circular cross section, in particular a square cross section, as shown in the example provided in the figures, or a rectangular cross section. Furthermore, preferably, the cross section of the holes 28 is slightly flared at the ends thereof facing the inside of the chamber S, as may be noted, for instance, in FIGS. 3, 4 and 8. In the case of the embodiment illustrated in FIGS. 2 to 8, each of the two half-chambers defined by the diaphragms 25A is provided with an equal number of holes 28, namely five.

As may be noted, therefore, the body 20 of the regulator RF has:

-   -   a first inlet section, designated by SI in FIG. 3 formed by the         top portion of the outer wall 21;     -   a narrowing or necking for passage and regulation of the liquid         made by means of the annular part 22A, which projects towards         the inside of the body 20;     -   a chamber, designated by S in FIG. 3 underlying the         aforementioned narrowed part and having a section substantially         the same as the latter, defined by the tubular wall 22A, the         bottom 23, the pin 24, the supports 25, and the membrane 26; in         the case provided by way of non-limiting example in FIGS. 2 to         8, the said chamber S is, in turn, divided into two         half-chambers by means of diaphragms 25A; and     -   a plurality of outlet ports of small cross section formed by the         holes 28.

According to the invention, the body 20 of the flow regulator RF is entirely obtained from thermoplastic material by means of a simple operation of moulding by virtue of the fact that the configuration proposed for the body 20 does not present a complex shape and/or complex undercuts. In order to obtain the body 20 it is therefore possible to use moulds for thermoplastic material of simple structure and contained cost.

Operation of the device RF according to the invention, in combination with the solenoid valve 1 of FIG. 1 is described in what follows.

With the solenoid valve 1 closed, i.e., with the solenoid 7 not energized, the liquid present in the inlet pipe 3 and in the area A is at the pressure of the mains supply, which is greater than the pressure existing in the outlet pipe 4. The liquid in the pipe 3 may reach, by means of the aforementioned calibrated holes of the membrane 14, the chamber C. The pressure, which is greater in the chamber C than in the outlet pipe 4 maintains the membrane 14 and the cup 13 in the condition which closes the passage that sets the area A in communication with the outlet pipe 4.

In order to enable passage of the liquid, the solenoid valve 1, which is of the normally closed type, must be activated in opening by supplying the solenoid 7. For this purpose, the solenoid valve 1 is electrically connected to the washing machine governed by it, which, by means of a programmer of its own, sees to controlling at the right moment (for example, at the start of a washing step) supply of the solenoid 7 by means of the terminals 9.

When the solenoid 7 is supplied, the mobile core 11 is attracted, so opening the central hole 12 of the cup 13. This enables the liquid present in the chamber C to be brought to the same pressure as the one present in the outlet pipe 4 (which, as has been said, is at a pressure lower than the incoming liquid arriving from the pipe 3 and/or present in the area A), under the thrust of which the membrane 14 and the cup 13 move so as to open the passage between the area A and the outlet pipe 4.

In the course of its passage of from the inlet pipe 3 to the outlet pipe 4, the flow of the liquid is stabilized and regulated by means of the membrane 26 of the regulator, according to modalities in themselves known.

It may be noted that, on account of the presence of the membrane 26, the pressure of the liquid entering the pipe 3 remains greater than that of the liquid leaving the pipe 4. Furthermore, on account of the geometry of known flow regulators, on the corresponding outlet there are present high levels of turbulence. These are the chief causes of the noise that is heard following upon opening of the solenoid valve in the case where appropriate silencing means are not provided, as mentioned in the introductory part of the present description.

In the case of the present invention, the fact that the flow regulator RF integrates directly the chamber S immediately downstream of the membrane 26, together with the plurality of holes 28 of small cross section in the bottom 23, enables the liquid passing in the flow regulator itself to assume a pressure that is intermediate between the pressures present in the pipes 3 and 4 and/or the flows to be stabilized, thus making it possible to render passage of the flow silent.

In the case of the present invention, the membrane 26 is supported centrally by the pin 24, and hence the flow of liquid entering the flow regulator RF enters the chamber S in a radial way passing underneath the membrane itself from its outer edge. In greater detail, in the context of the flow of liquid passing inside the regulator RF, it is possible to identify a number of successive stretches, namely:

-   -   a first flow stretch, which is axial in the chamber SI;     -   a second flow stretch, which is radial from the outside towards         the centre underneath the membrane 26; and     -   a third flow stretch, which is axial in the chamber S, which is         then divided, by means of the holes 28, into a number of partial         axial flows, the said partial flows remaining substantially         axial until they recombine in the area A of the pipe 3.

When, subsequently, the solenoid 7 is de-energized, the mobile core 11 returns into its original position so that the plug 10 will close the central hole 12 of the cup 13 again. In this condition, the chamber C returns to a pressure higher than the one present in the outlet pipe 4, so causing a movement of the membrane 14 and of the cup 13 into the position where the passage between the chamber A and the outlet pipe 4 is closed. There is thus a return to the initial conditions.

From the description provided above, as well as from the attached claims, which form an integral part thereof, the characteristics of the present invention emerge clearly, as do the corresponding advantages, namely:

-   -   the flow regulator RF according to the invention directly         integrates a silencing arrangement and can be made of a single         body, to which is associated the respective membrane, which may         be obtained by means of a simple process of moulding of         thermoplastic material at contained production costs;     -   the fact that the flow regulator according to the invention         directly integrates silencing means rules out the need, which is         typical in the known art, of having to provide a specific         operation for assembly of a purposely built and distinct         silencing insert;     -   the fact that the flow regulator according to the invention         directly integrates the silencing means likewise prevents the         risk, which is typical in the known art, that the said silencing         means may change position or their distance apart from one         another and hence cause variations in the operating         characteristics.

It is clear that numerous variants are possible for the person skilled in the art to the device described by way of example, without thereby departing from the scope of the inventive idea.

In the case of FIGS. 9 to 11, in which the references appearing in the foregoing figures are used to designate elements that are technically equivalent to the ones already described, there is for example represented a flow regulator RF, the body 20 of which is provided with four ribs or diaphragms 25A so that the chamber D will be divided into four half-chambers. In the case of the said variant, a single hole 28 is provided for each half-chamber.

In the case of the variant illustrated in FIGS. 12 to 14, instead, even though there are once again provided four diaphragms 25A, a different distribution, i.e., non-specular distribution, of the holes 28 is envisaged. If need be, this arrangement may be provided in order to compensate for any possible distributions of the flow of the liquid in the regulator RF due to the different distributions of the calibration projections 27, which tend to keep the membrane 26 more raised and hence to concentrate the regulated flow in that area.

The diaphragms 25A, irrespective of their number, may be provided should the aim be to contain or prevent formation of any turbulent or circular flow inside the flow regulator RF. The said diaphragms may therefore advantageously operate as a preliminary diffusor and may be appropriately shaped for this purpose, as well as possibly contributing to the reinforcement of the central pin 24.

It should however be noted that, in accordance with a further possible embodiment of the invention, an example of which is represented in FIGS. 15 to 17, the diaphragms 25A could be completely omitted, given that the pin 24 and the supports 25 are, in any case, supported by the bottom 23, which is, in turn, integral with or fixed to the internal tubular wall 22B, the latter being supported or fixed by means of the annular wall 22A directly by the external wall 21 of the body 20.

According to a further possible variant, the annular wall 22A could have a thickness that is decidedly greater than the one illustrated in the attached figures so that its central or internal hole may replace the annular wall 22B. In this variant, the bottom wall 23 would therefore be attached to the wall 22A or else to the outer wall 21.

In other possible variants of the invention, there could be provided radial ribs or diaphragms between the outer wall 21 and the inner tubular wall 22B and/or between the bottom wall 23 and the outer wall 21.

Instead of a disk membrane of the type designated previously by 26, the device RF according to the invention could envisage flow-regulating means of a different type, in accordance with techniques in themselves known, such as an O-ring or a mobile cup with a spring.

In accordance with a further possible variant, the flow regulator RF could be conceived for operating also as a filter. In this perspective, in order to prevent any possible early clogging thereof, there could be provided an adequate or greater number of holes 28 within the chamber S. The said holes will be appropriately sized, as regards their number and their location, by possibly providing some of them also on the wall 22B of the chamber S (which may be more elongated than what is shown in the case of the example provided previously), as well as on the bottom 23. In order to facilitate moulding of the said lateral holes on the wall 22B, the bottom part of the outer wall 21 could be absent or else modified with respect to what has been illustrated. 

1. A device for regulating and stabilizing a flow of a fluid, in particular for solenoid valves, envisaged for insertion in a pipe for passage of the fluid (3), said device (RF) defining internally at least: one inlet passage (SI), having a first section; a section narrowing (22A) downstream of said inlet passage (SI), flow-regulating means (26) being provided in correspondence of said narrowing, in particular a membrane (26); and supporting means (24, 25) for said flow-regulating means (26), in correspondence of said narrowing (22A); wherein said device (RF) further defines, downstream of said narrowing (22A) and said flow-regulating means (26), a chamber (S) having a cross section smaller than that of said inlet passage (SI), said chamber (S) being delimited at its longitudinal end opposite to said flow-regulating means (26) by a bottom wall (23), wherein said device (RF) comprises a single body (20), said inlet passage (SI) is defined by an external wall (21) of said single body (20), in particular a substantially cylindrical or tubular wall which surrounds at least partly said flow-regulating means (26), and said chamber (S) is provided with a plurality of outlet passages (28) having a section smaller than that of said chamber (S).
 2. The device according to claim 1, wherein a plurality of said outlet passages (28) is defined in said bottom wall (23).
 3. The device according to claim 1, wherein said supporting means (24, 25) comprise at least one pin element (24), which rises from said bottom wall (23) towards the inside of said body (20).
 4. :he device according to claim 1, wherein said supporting means (24, 25) comprise at least one pin element (24), supported by said bottom wall (23).
 5. The device according to claim 1, wherein said supporting means (24, 25) define internally at least one blind hole.
 6. The device according to claim 1 or claim 3, wherein said supporting means (24, 25) comprise one or more projections (25), which rise from said bottom wall (23) towards the inside of said body (20), where, in particular, at least one portion of said regulating means (26) is fixed or extends on top of said projections (25).
 7. The device according to claim 6, wherein said supporting means (24, 25) comprise at least one pin element (24), supported by said bottom wall (23) and said projections (15) are formed in opposite areas to said pin element (24).
 8. The device according to claim 1, wherein said outlet passages (28) are defined in lateral areas of said bottom wall (23), said supporting means (24, 25) rising from a central area of said bottom wall (23).
 9. The device according to claim 1, wherein said outlet passages (28) have a non-circular cross section, in particular a square or rectangular cross section.
 10. The device according to claim 1, wherein a cross section of said outlet passages (28) is flared at an end thereof facing the inside of said chamber (S).
 11. The device according to claim 1, wherein said chamber (25) has at least one internal subdivision element (25A).
 12. The device according to claim 11, wherein a number of subdivision elements is provided, in the form of internal diaphragms (25A) of said chamber (S), each extending radially starting from said supporting means (24, 25).
 13. The device according to claim 11, wherein said chamber (S) is divided, by means of two or more of said subdivision elements (25A) into two or more half-chambers.
 14. The device according to claim 13, wherein said half-chambers have an equal number of said outlet passages (28).
 15. The device according to claim 13, wherein said half-chambers have a different number of said outlet passages (28).
 16. The device according to claim 4, wherein said regulating means comprise a membrane (26) having a central hole (26A) fitted on said pin element (24), where part of a bottom surface of said membrane (26) near said hole (26A) is locally resting upon a top surface of said projections (25).
 17. The device according to claim 1, wherein rising from one surface of said narrowing (22A) are relieves or spacers (27) for said regulating means (26), in particular having a circular cross section.
 18. The device according to claim 17, wherein said regulating means comprise a membrane (26) and said relieves (27) constitute points of local support for at least one part of a bottom surface of said membrane (26) near an external diameter of the latter.
 19. The device according to claim 17, wherein a number of said outlet passages (28) is more concentrated in areas of said bottom wall (23) to which there correspond areas of said narrowing (22A) where said relieves (27) are defined.
 20. The device according to claim 1, wherein an annular wall (22A) branches off from said external wall (21), towards the inside of said body (20), said annular wall (22A) defining said narrowing, said annular wall extending in a direction substantially orthogonal to said external wall (21).
 21. The device according to claim 20, characterized in that from an internal end of said annular wall (22A) a tubular wall (22B) branches off, which extends towards an end of said body (20) opposite to an end in which said regulating means (26) are positioned.
 22. The device according to claim 21, wherein said tubular wall (22B) is substantially orthogonal to said annular wall (22A).
 23. The device according to claim 21, wherein said bottom wall (23) is provided at a bottom end of said tubular wall (22B).
 24. The device according to claim 2, wherein at least one wall (24, 25) of said body (20) rises centrally from said bottom wall (23) within said chamber (S), said outlet passages (28) being defined in an area of said bottom wall (23) not occupied by said at least one wall (24, 25).
 25. The device according to claim 20, wherein said external wall (21) has a passage section that decreases progressively, from a part of said body (20) in which said regulating means (26) are arranged up to said annular wall (22A).
 26. The device according to claim 20, wherein said external wall (21) has an internal diameter that increases progressively from said annular wall (22A) up to a part of said body (20) opposite to a part in which said regulating means (26) are arranged.
 27. The device according to claim 21, wherein a section of said tubular wall (22B) decreases progressively from said annular wall (22A) up to said bottom wall (23).
 28. The device according to claim 1, wherein said body (20) is entirely obtained in a single piece of moulded thermoplastic material.
 29. The device according to claim 20, wherein radial connection elements or baffles are provided between said bottom wall (23) and said external wall (21).
 30. The device according to claim 21, wherein radial connection elements or baffles are provided between said tubular wall (22B) and said external wall (21).
 31. The device according to claim 1, wherein said outlet passages (28) are provided also for the purpose of filtering the fluid.
 32. The device according to claim 1, characterized in that outlet passages are provided also on at least one side wall (22B) of said chamber (S) or in said annular wall (22B).
 33. A hydraulic valve having a respective body defining an inlet pipe (3), an outlet pipe (4), open/close means (13, 14) set operatively between said inlet pipe (3) and said outlet pipe (4), actuator means (7), which are operative for producing switching of said open/close means (13, 14), the valve further comprising, within at least one of said pipes (3, 4), a device for regulating and stabilizing a flow of a fluid (RF) built according to claim
 1. 34. The valve according to claim 33, wherein is a solenoid valve of the unbalancing type or servo type.
 35. The valve according to claim 33 or claim 34, wherein, upstream of said flow-regulator device (RF), a filter (6) is present in said pipe (3).
 36. A method for regulating and/or stabilizing a flow of a fluid, with the simultaneous reduction of the noise of the latter, by means of a flow regulator (RF) having a body (20) that is mounted in a pipe (3) and has an axial direction in said pipe (3), wherein, within the body (20) of the flow regulator (RF), a flow of fluid is induced to follow: a first path section, which extends axially in an inlet passage (SI) of the body (20) of the regulator (RF); a second path section, which extends radially, in particular from the outside towards the centre of the body (20) of the regulator (RF), between a section narrowing (22A) which is downstream the inlet passage (SI) and flow-regulating means (26); and a third path section, which extends axially in a chamber (S) which has a section smaller than that of the inlet passage (SI) and is defined downstream of the regulating means (26) and the section narrowing (22A); wherein the flow of the fluid, at the end of the third path section, is divided into a number of partial flows, by means of a plurality of openings (27) defined in a bottom (23) of said chamber (S), said partial flows recombining at the outlet of said openings (27). 